The Central Indian Tectonic Zone (CITZ) formed during the Mesoproterozoic north-south collision between the Bundelkhand and Bastar Cratons. The origin of the deformation of the Late-Paleoproterozoic Lower Vindhyan Group (LVG), which occurs in the sedimentary basin adjacent to and north of the CITZ, is debated, with previous researchers supporting synsedimentary processes. To investigate the possibility of a collisional origin, we collected and analysed litho-structural data from the LVG and the Mid-Paleoproterozoic Mahakoshal Supracrustal belt (MSB), which lies within the CITZ. We report, for the first time, diverse structures from the LVG, such as various types of buckle folds including kink-folds, reverse faults and, most importantly, 5–20 meters long outcrops of pop-up structures, which are commonly encountered in fold-thrust belts. However, the adjacent MSB showes relatively complex polyphase deformation with three major deformation stages that produced: (i) E-W-trending regional foliation and diversely oriented folds (D1), (ii) E-W oriented steep folds associated with a large-scale shear zone along the Son-Narmada South Fault (D2) and (iii) local cross-folds (D3). Based on our field observations in the LVG and the MSB, we additionally propose and substantiate, through geological cross-sections and a kinematic model, that the LVG deformed between the D3 and the deposition of the Upper Vindhyan Group. Unlike previous studies, which attributed the deformation structures of the LVG to seismic or soft-sediment processes, our findings confirm that the Mesoproterozoic collision along the CITZ deformed the LVG as the deformation front, aided by detachment folding, propagated into it.

A new species of flatfish (Pleuronectiformes) is described from early Oligocene deposits of the Keasey Formation near Mist, Oregon, USA. The rare preservation of an articulated fish in the Mist crinoid lagerstätte is likely because the specimen represents a relatively pelagic immature individual that had not yet settled into the typical benthic lifestyle of adult flatfishes. The new species is included in a phylogenetic analysis; although it is lacking many characters, it is recovered as an early diverging lineage, sister to the extant members of the superfamily Pleuronectoidea. This phylogenetic position fits well with the age of this fossil and conforms with the origin of flatfishes occurring in the early Cenozoic, followed by diversification and radiation throughout the Eocene, Oligocene and Miocene epochs.

The limestone and marlstone succession of the Pliensbachian Vale das Fontes and Lemede formations at the Global Boundary Stratotype Section and Point (GSSP) at Peniche (Portugal) received much attention in numerous studies. It contains abundant pyritic and limonitic aggregates, which are herein described and interpreted as remarkably preserved soft-bodied organisms (worms) for the first time. The slender to compact bodies with a cylindrical or dorsoventrally flattened cross-section are several centimetres long and have a diametre/width of 0.5–8 mm. They occur on bedding planes or are partly preserved within their burrows. Although their taphonomic history did not favour the preservation of many details, key features such as body shape, size and composition, as well as occasionally preserved segmentation and body appendages, allow a rough assignment to the phyla Nemertea, Annelida and Nematoda. Favourable circumstances such as intermittent dysoxic to anoxic bottom conditions, microbial activity and sudden burial have probably contributed to a reduced decay of the soft bodies. Comparison with similar successions globally shows that such a preservation of worms is not a unique process but occurs in several thick, fine-grained units throughout the Phanerozoic. Such inadequately preserved soft-bodied animals are still often overlooked but have the potential to add to our knowledge of the distribution and evolution of major clades of non-skeletal organisms.

This study examines detrital garnet compositions from five samples spanning a Late Miocene–Pliocene section of Himalayan sedimentary rocks (Surai Khola, Siwalik Group and central Nepal) to assess provenance and tectonic implications. A total of 100 detrital garnets were analysed for edge-to-edge compositional zoning, revealing distinct groups linked to specific hinterland regions. Manual classification identified garnet Groups 1 and 2 as grossular, Group 3 as spessartine, and Groups 4 through 7 as almandine, varying in XCa, XMg and XMn. Most garnets exhibit low XMg and flat zoning, with Groups 6* and 7* containing slightly higher XMg. Statistical clustering aligns broadly with manual groupings, which strengthens provenance interpretations. Comparisons with hinterland garnet compositions expand provenance options to magmatic garnets and rocks outside the Himalayan core units. Eight Siwalik Group garnets were modelled for pressure–temperature conditions and paths. Group 4 and 6 garnets, potentially linked to blueschist/eclogites or metamorphosed arc/Himalayan core rocks, record conditions of 510–538°C and 4.6–6.8 kbar, with isothermal burial over 0.5–2 kbar. Group 2 garnet, resembling compositions from North Himalayan granitic enclaves, yields core conditions of 480°C and 6 kbar and an N-shaped pressure–temperature path. Two Group 5 garnets with zoning like those in the High Himalayan leucogranites yield 520–528°C at 3.2–3.6 kbar. These findings provide insights into Himalayan erosion dynamics, hinterland exhumation and sediment transport pathways. Integrating garnet compositional zoning with statistical clustering and thermodynamic modelling is valuable for provenance studies of garnet-bearing sedimentary sections.

The first precise, biostratigraphically bracketed U-Pb dates on the middle Middle Cambrian come from the Rte. 111 ash (new) in the lower Manuels River Formation of southern New Brunswick. Manuels River black mudstone (Avalonian depositional sequence [Ads] 8) unconformably overlies Fossil Brook Member greenish mudstone (Ads 7) of the Chamberlain’s Brook Formation, and the two units should not be combined into a ‘Forest Hills Formation’ (abandoned). This unconformity marks the trans-Avalonian (i.e., Rhode Island–Belgium) green–black boundary and onset of ca. 26 Ma of dysoxic/anoxic marine deposition. Trilobites and agnostids correlate the surprisingly endemic, upper Paradoxides abenacus Zone and Rte. 111 ash into the Hypagnostus parvifrons Zone (Drumian) in Avalonian Wales, Baltic upper ‘Acidusus’ atavus Zone and upper Mawddachites hicksii–lower Paradoxides davidis zones of Avalonian Newfoundland and Britain. The Manuels River Formation in SE Newfoundland and coeval Nant-y-big Formation in South Wales have not yielded ash dates. However, our U-Pb zircon analyses of the Rte. 111 ash in the lower Manuels River in southern New Brunswick yield statistically identical ages of 501.44 ± 0.10 and 501.45 ± 0.08 Ma. The Ads 7–8 unconformity is locally 6–10 m lower in New Brunswick and is somewhat older. Our ages for the Rte. 111 ash show the lower Drumian is significantly younger than previous estimates, is ca. 4.9 Ma younger than the Lower–Middle Cambrian boundary, and debunks claims of a continuous Lower–Middle Cambrian succession in Avalonian New Brunswick where a ca. 7 Ma hiatus is present.

The Guanajuato Mining District of central Mexico is one of the main silver and gold deposits in the world. It is in the State of Guanajuato in the southern part of the Sierra Madre Occidental (SMO) volcanic province. The mining district developed within a mid-Tertiary volcano-sedimentary sequence that includes thick alluvial-fan deposits accumulated in a tectonic basin during the Eocene-Oligocene named the Guanajuato Red Conglomerate and an overlying volcanic sequence mostly pyroclastic of Oligocene age. The mid-Tertiary stratigraphy of Guanajuato is revised and reinterpreted in the light of new fieldwork and U-Pb ages, which document a close timing between all units of the volcanic succession at the top of the Guanajuato Red Conglomerate. This sequence is made of pyroclastic density current deposits formed during episodic events from the Guanajuato caldera. A new nomenclature of the caldera’s units is proposed; the Guanajuato Caldera Volcanic Group, which includes the Guanajuato Pyroclastic Formation represented by the Loseros PDC deposits and the Bufa-Calderones ignimbrites emplaced around 32.8 ± 0.2 Ma, and the post-collapse lava domes of El Rodeo and Chichíndaro formations emplaced at 31–30 Ma. Apparently, a resurgent pulse of the caldera uplifted the collapsed intra-caldera blocks, so that the caldera floor is now exposed. The caldera collapse was controlled by the pre-existing normal faults inherited from the previous tectonic basin; thus, it is classified as a graben-type caldera, with a square shape and a size of 15 × 16 km. By comparison with other similar calderas of Mexico, the Guanajuato caldera is another case study of graben-type calderas of the SMO coinciding with mineral districts, such as Bolaños (Jalisco).

Magnetostratigraphy, palynology and ammonite biochronology of the Staithes S-20 core are used in an integrated evaluation of the late Norian to early Hettangian successions in Britain. The polarity patterns of the Blue Anchor and Westbury formations differ from their counterparts in SW England, indicating younger and older ages, respectively, for those units in NE England. Magnetostratigraphy indicates an underlying Sevatian age hiatus coeval with the D5 disconformity of the German Keuper. The miospore succession from S-20 is divisible into zones like those from the St Audrie’s Bay section in SW England. Using magnetic susceptibility datasets for the earliest Hettangian chronozones from S-20, Lavernock, St Audrie’s Bay and Lyme Regis, a new method is used to derive a TimeOpt-based astrochronology for the earliest Hettangian. This is anchored to radioisotopic dates from Peru correlated into British sections using carbon isotope excursions. A brief reverse magnetozone in the basal Cotham Member in the Staithes S-20 core and the astrochronological evaluation demonstrate that CAMP volcanics are coeval with the end-Triassic extinction in UK sections. An eco-plant model assessment of the miospores indicates greater proportions of eurythermic and europhyte floras, suggesting stronger seasonality in palaeoclimate was probably a key factor in the end-Triassic extinction.

The Deerni copper deposit is one of the largest in Qinghai province, China, with proven copper reserves of 0.556 Mt. To explore new copper orebodies, we conducted a geological study at western Deerni focusing on hydrothermal alterations and ore-controlling structures. Field investigation shows that the deposit is hosted mainly within the central segment of the Deerni ophiolite. Additional hosts include Lower-Permian slate, limestone, gabbro and volcanic rock, as well as the contact zone between granite and slate. Such observations indicate that the Deerni copper deposit is not only associated with the ophiolite, but its formation is also controlled by faults. Alterations including serpentinization, carbonatization, silicification and malachite, and magnetite mineralization occurred along fractures within the wall rocks and surrounding strata. This means the alteration post-dated structural activity that affected the Lower Permian strata in the region. The Deerni copper deposit is controlled by the NW-striking faults. This is evidenced by (1) slate fragments and breccias within the orebodies, (2) saw-toothed boundaries between the orebodies and host rocks, (3) copper ore veinlets and (4) striations and step patterns on the orebody surface and hanging-wall-hosted quartz veins. Mineralization controlled by NW-trending faults suggests a major orebody (‘No. 2’) likely extends to either northwest or southeast. Field investigations along with geophysical and geochemical data, thus predicted the presence of concealed copper orebodies in western Deerni. Subsequent drilling projects have verified this prediction and revealed three concealed orebodies with widths of 7.15–13.87 m and Cu grade of 1.00–11.34 wt.%, adding 10,000 tonnes to the copper reserves.

Ichnological studies in deep-marine successions are of great use for detailing the evolution of these sedimentary environments, as well as highlighting the changes in ambient conditions. In order to investigate these aspects, the deep-marine Maghrebian Flysch Basin of Northern Morocco was chosen for study. Within this basin, two sedimentary successions – the Beni Ider and Tala Lakrah units, comprising calcareous and siliciclastic turbidite sediments and ranging in age from Late Cretaceous to Early Miocene, were examined in detail. An ichnoassemblage (31 ichnogenera, 41 ichnospecies), including 9 graphoglyptid ichnogenera, was recognised, with the ichnoassemblages belonging to the Nereites ichnofacies. Pre- and post-depositional ichnofossils were present in equal amounts, with ichnodiversity being higher in Eocene times.

Comparison and correlation of the ichnological data from Morocco (this study) with data from Spain indicated that the main influences on trace fossil distribution within the successions were broadly similar. Environmental factors, such as substrate, oxygen and nutrient contents, as well as the ambient hydrodynamic regime and the frequency and intensity of turbiditic events, all played an important role. However, the relative importance of these factors varied both spatially as well as temporally within the different parts of the Maghrebian Flysch Basin. Temporal variations were related both to changes in (orogenically-influenced) basin and lobe evolution, as well as changes in global oceanographic and climatic conditions at the Eocene–Oligocene transition.

We present the mineralogy and whole rock geochemistry of the lamproites dykes from the Kawardha area of the Western Bastar Craton. These dykes are characterized by phenocrysts and microphenocrysts of olivine, phlogopite, ulvo-spinel, Cr-spinel and magnetite within the chlorite and carbonate-rich groundmass with rutile and apatite as accessory phases. Mineral chemistry indicates that the lamproites in Kawardha are similar to olivine-phlogopite lamproites and are geochemically similar to other lamproites in the eastern Bastar craton. The Kawardha lamproites are characterized by higher concentrations of MgO (12–20.29 wt%), V (193–502 ppm), Ni (206–823 ppm), Cr (146–1130 ppm), Nb (101–260 ppm), Zr (301–635 ppm), Hf (6–13 ppm) and LREEs. Positive Nb-Ta anomalies and Th, Hf and Zr variations are comparable to other intra-cratonic rift-related lamproites. The geochemical variations (such as REE, HFSE and LILE) are consistent with an asthenospheric mantle source similar to the other lamproites in Bastar craton. Trace element modelling implies a low-degree partial melting (0.1–2%) of phlogopite-bearing garnet-lherzolite and/or phlogopite-bearing spinel-lherzolite mantle source. The widespread Proterozoic rifting events in the Bastar craton likely led to the melting and upwelling of the asthenospheric mantle and which further interacted with the metasomatized lithospheric mantle to form the parental melts of the lamproite dykes of the Kawardha area.

The present study documents the lithostratigraphy, biostratigraphy, facies evolution and depositional environments of the Eocene El Kohol Formation exposed on the southern flank of the Central Saharan Atlas (Algeria), through the integration of lithological characteristics, fossil and ichnofossil assemblages, and microfacies analysis. The succession is subdivided into two formal members: the Marly El Kohol Member, comprising a lower marlstone-dominated interval, and the Siliciclastic Kheneg ed Dis Member, representing an upper sandstone-dominated succession. The boundary between these members is marked by a transition from pale, carbonate-rich deposits to darker clastic sediments.

Field observations and microscopic analyses have enabled the recognition of sixteen facies types (Ft1–Ft16), which are interpreted in terms of depositional environment and grouped into four main facies associations (FA1–FA4): (FA1) an inland lake environment; (FA2) a palustrine environment, characterized by carbonate deposition in freshwater to brackish conditions with subaerial exposure and paedogenic modification; and alluvial settings comprising (FA3) fluvial channel and (FA4) floodplain deposits.

Palaeontological analyses have produced new micropalaeontological data for the region, including charophytes (Sphaerochara parvula, Nodosochara [Turbochara] sp., Gyrogona sp., Harrisichara cf. leptocera, Lamprothamnium papulosum, Peckichara torulosa var. varians, Raskyella cf. sahariana and Nitellopsis cf. [Tectochara] dutempleii), ostracods (Neocyprideis meguerchiensis, Paracypris? sp. 1, Paracypris? sp. 2 and Thalassocypria? sp. 1) and actinopterygian fish microremains (primarily from polypterids and alestids). Additionally, fragmentary remains of the terrestrial proboscidean Numidotherium koholense have been recovered. Ichnological analysis of the succession identified five ichnotaxa: Ophiomorpha isp., Palaeophycus isp., Skolithos annulatus, Skolithos linearis and Thalassinoides horizontalis.

This study contributes to refining the regional and North African understanding of the spatial extent and palaeoenvironmental evolution of the Eocene succession and helps to complete the ichnological and palaeontological records of the Eocene in the area.

As international exploration of the Meso-Neoproterozoic continues, these layers have become a key target for deep oil and gas field exploration. The Ordos Basin exhibits considerable sedimentary thicknesses within the Meso-Neoproterozoic. However, significant hydrocarbon discoveries have not been forthcoming, primarily due to the complex tectonic evolution. This paper focuses on the southern Ordos Basin, utilizing logging-seismic calibration to interpret seismic data and elucidate Meso-Neoproterozoic tectonic features. By comparing ancient and modern tectonic patterns, based on palaeotectonic maps retrieved through the impression method and combining these with tectonic evolution profiles, the study clarifies the history of tectonic modification. Under the control of two fracture systems – basin-controlling fractures at the margin and trough-controlling fractures – the Changchengian exhibits two categories (single-fault and double-fault) and five sub-categories of fault depression combinations. The study highlights significant differences between ancient and modern tectonics in the Meso-Neoproterozoic, which are attributed to various tectonic stages, including the trough-uplift depositional differentiation stage during the early rift-late depression of the Changchengian, the basin-margin subsidence stage of the southwestern depression of the Jixianian, the uplift and denudation stage of the Sinian basin’s main body and the four-stage tectonic remodelling stage of differential uplift-subsidence in the Palaeoproterozoic. This study employs the ancient-present tectonic pattern as a point of departure, thereby enhancing the theoretical understanding of deep-seated tectonics in the Ordos Basin. It offers novel insights into the exploration of Meso-Neoproterozoic gas reservoirs from a tectonic remodelling perspective.

Carbonatites are complex rocks yet globally significant hosts of critical mineral resources. Mitigating exploration risk demands robust understanding of their geodynamic setting, which hinges on constraining the timing, duration and nature of associated magmatic and fluid–rock processes. We present multi-method geochronology and isotope geochemistry for the recently discovered Luni and Crean mineralized (Nb, REE, P) carbonatites of the Aileron Province, central Australia. We integrate data from multiple mineral-isotope-pairs: U–Pb and Lu–Hf in zircon, Rb–Sr in biotite and Sr, Lu–Hf, Sm–Nd and (U–Th)/He in apatite. Combined petrological and isotopic evidence resolves distinct geological events over >500 Myr. Zircon U–Pb and biotite Rb–Sr dates range from 831 ± 3 Ma to 796 ± 9 Ma. The oldest dates from less altered minerals reflect primary crystallization, and younger dates relate to pervasive hydrothermal alteration. Radiogenic isotopes (Sr–Nd–Hf) imply a moderately depleted mantle source with negligible recycled sedimentary components in the primary carbonatite magma. Our findings correlate carbonatite magmatism in the Aileron Province at ∼830–820 Ma with the onset of Rodinia Supercontinent breakup, during widespread rift-related extension and mantle-derived magmatism across Australia. Post-emplacement, Lu–Hf apatite dates from 722 ± 17 Ma to 653 ± 22 Ma suggest protracted alteration, whereas apatite (U–Th)/He data indicate exhumation at ∼250 Ma. Carbonatite emplacement probably exploited pre-existing transcrustal corridors during Tonian extension. These zones of structural weakness likely facilitated ascent of volatile-rich, mantle-derived melts to mid–shallow crustal depths, highlighting how regional geodynamics govern the localization and preservation of mineralized carbonatites.

Folds within layered rock systems are critical for comprehending the historical processes of deformation and the rheological behaviour of rocks. The current study employs finite element modelling to investigate the development of folds in a layered rock system, with a particular focus on the impact of thinner layers on the folding of adjacent thicker layers and their subsequent interactions. The analysis indicates that harmonic folds can evolve into polyharmonic or disharmonic configurations because of the intricate interactions occurring within the contact strain zone of the thinner layer. Our numerical findings demonstrate that the geometry of folds is significantly affected by the reciprocal interactions between thinner and thicker layers, initiated by the folding of the thinner units and their consequent influence on the thicker layers, and vice versa. This dynamic interplay, however, may frequently diverge from predictions made by more simplistic models, as suggested by earlier studies. Furthermore, this research highlights the potential of utilizing higher-order fold geometries to estimate the relative viscosity between the layers and the embedded medium.

Investigating magmatic processes in exhumed lower continental crust is often complicated by metamorphic and tectonic overprints postdating magma emplacement. To decrypt these requires integrated structural and petrological analyses at multiple scales. This study provides a new Virtual Outcrop Model (VOM) combined with structural and petrographic analyses of a ∼83 m long outcrop within the Mafic Complex of the Ivrea-Verbano Zone (IVZ), Italy, representing an exhumed section of the lower continental crust. The outcrop is mainly composed of hornblende gabbronorites with variabilities in garnet textures and modal abundances. The main foliation shows local changes in orientation but is generally sub-parallel to the Insubric line. We identify previously unreported olivine-hornblende garnetite and garnet hornblendite lenses, often associated with anorthosite lenses by gradual contacts. Garnet-olivine gabbro occurs in the northern and southern zones of the outcrop. A metamorphic overprint is indicated by: (i) granoblastic to polygonal textures with triple junctions, (ii) rutile exsolution in orthopyroxenes, (iii) hercynite exsolution in plagioclase and (iv) coronitic garnet formed around oxides and olivine. Previously unreported mafic pegmatites crosscut by pseudotachylytes were also identified. Alpine-related faults and shear structures crosscut all lithologies, but detailed field observations combined with analyses of the VOM facilitated the conclusion that the original, pre-alpine spatial relationships between the different magmatic units have not been significantly altered. The lithological sequence and mineralogical variability of this outcrop can, therefore, be used for future detailed studies to assess the primary magmatic processes and subsequent metamorphic pressure-temperature path that affected this portion of the lower continental crust.

Two assemblages of Floian graptolites from the Acoite Formation at a new section on the western flank of the Cordillera Oriental, Jujuy Province, referred to as El Moreno, are presented. The first assemblage includes Acrograptus spp., Baltograptus jacksoni Rushton, Baltograptus cf. jacksoni Rushton, Baltograptus sp. and poorly preserved tetragraptids. The second assemblage comprises Baltograptus deflexus? (Elles & Wood) and Baltograptus minutus (Törnquist). The presence of Baltograptus jacksoni and Baltograptus minutus allows for the identification of the eponymous biozones, indicating a middle to late Floian age for the studied strata. This contribution confirms the occurrence of Baltograptus jacksoni in Argentina. In addition, previous records of Floian graptolites from northwestern Argentina are revised, thus supporting the proposal to use the Baltograptus jacksoni and Baltograptus minutus zones in the Cordillera Oriental of Argentina. This enables regional correlations with equivalent levels throughout the Central Andean Basin, as well as more precise intercontinental correlation.

The Spence Shale of Utah and Idaho preserves a diverse soft-bodied biota from the Cambrian. While the fauna is dominated by arthropods and echinoderms, soft-bodied animals belonging to other groups are known. Here we document Tentalus spencensis gen. et sp. nov. from the High Creek locality of the Spence Shale. The fossil has a crown of short stubby tentacles and appears to have been attached to the sediment through a stalk. The morphology of Tentalus suggests that it is a dinomischiid or deuterostome; however, it cannot be attributed to any of the known species, based on the short and conical tentacles surrounding an oral region, and polyp-like oblong columnar trunk terminating in a stalk, that do not resemble any described species.

Garnet and biotite are common minerals in and adjacent to metamorphosed massive sulphide deposits, but their trace element compositions are rarely used to explore for such ores. Both minerals are present in hydrothermal alteration zones metamorphosed to the amphibolite facies spatially related to semi-conformable massive sulphide horizons in the Paleoproterozoic Stollberg Zn-Pb-Ag-(Cu-Au) plus magnetite ore field, Bergslagen district, Sweden. The major-trace element chemistry of garnet in metamorphosed altered rocks, mafic dykes and sulphide mineralisation shows that garnet in garnet-biotite alteration (and high-grade sulphides) is Fe-rich (almandine ratio > 0.5) whereas garnet in skarn and garnet-pyroxene alteration contains significantly higher amounts of Ca and Mn and elevated concentrations of Co, Cr, Ga, Ge, Sc, Ti, V, Y, Zn and the heavy rare earth elements (HREEs). Chondrite-normalized REE patterns of garnet in all rock types are depleted in light REEs and enriched in heavy REEs. Garnet in sulphide-bearing altered rocks, including garnet-biotite and garnet-pyroxene alteration, shows a strong positive Eu anomaly and the highest concentrations of Ga, Ge, Mn, Pb and Zn. Rocks more distal to sulphide mineralisation typically contain garnet that exhibits no or negative Eu anomalies and lower mean concentrations of these elements and higher concentrations of Ti. Biotite shows variable Fe/(Fe+Mg) ratios with most centred around 0.5 and enrichments in Ga, Mn, Sn, Pb and Zn in and adjacent to sulphides. This suggests that garnet and biotite can be used as a vectoring tool to ore in the Stollberg ore field and potentially for metamorphosed massive sulphides elsewhere.

Recent development in the Upper Ordovician conodont biostratigraphy of Baltoscandia highlights the mismatch between the traditionally used conodont zonation and ranges of the eponymous species. Practical application of the zonation is further complicated by the fact that the morphology of the long-ranging species Amorphognathus tvaerensis, the key taxon of the eponymous conodont zone, changes through its distribution interval, and its older and younger representatives are quite different. The latter one was recently described as a new species, A. viirae. Also, it appeared that the specimens assigned earlier to A. ineaqualis in the northern Baltoscandian region are conspecific with A. tvaerensis and A. ineaqualis is missing here. As a result, the A. ineaqualis Conodont Zone has to be abandoned from the regional zonal scheme. Restudy of conodont collections from the Bliudziai-150 (Lithuania) and Kovel-1 (Ukraine) core sections demonstrated the absence of A. ineaqualis and the presence of A. viirae also in the southern Baltoscandian area and Ukraine. This paper contains a formal description of the new, emended conodont zonation for Sandbian and the lowermost Katian of the Baltoscandian Palaeobasin and its correlation to the regional chemostratigraphic standard.